New `exclude` config field per target generates .josh-filters/<name>.josh
files with josh :exclude clauses. Josh-proxy applies exclusions at the
transport layer — excluded files never appear in the subrepo.
Preflight checks that generated filter files are committed.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
- README: add onboard and migrate-pr to CLI reference
- Guide Step 5: add onboard as recommended Option A, move manual
import/reset to Option B, document migrate-pr usage
- Guide "Adding a New Target": mention onboard as preferred path
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
